The present invention relates to a vacuum apparatus for treating workpieces in accordance with the generic term of claim 1.
Vacuum apparatuses for coating workpieces are known that feature a vertically arranged, cylindrical or polygonous vacuum chamber with process stations such as sputtering sources, etching devices or also heating devices arranged on the outer surfaces of said chamber, and with a cylindrical, rotative workpiece holder arranged around the central axis of said chamber, so that the workpieces can be incrementally or continually transferred across the various process stations. Such systems are frequently operated in so-called "batch mode" which means that several workpieces are placed simultaneously on the substrate holders and loaded through a vacuum lock into the system for subsequent processing.
Also known are systems with a cylindrical arrangement, such as described in U.S. Pat. No. 4,675,096 in which the workpieces are loaded and unloaded individually through the vacuum lock and processed in consecutive cycles. The system described in said patent is principally suited to small-surface workpieces. Large-surface workpieces which often are very thin and consequently delicate to handle, cannot readily be processed with such a system configuration. With the high process cycle frequencies required for economical operation, it is particularly difficult to find a configuration through which large-surface substrates can be reliably processed without breaking them.
For large-surface workpieces to be coated, systems have become known that are typically operated as so-called linear flowthrough or cyclic systems. In this type of system the process stations are arranged consecutively in a line and the workpieces are usually loaded through the vacuum lock at one face side and unloaded on the opposite side. Such a system is described, for example, in U.S. Pat. No. 4,663,009. For increasing the cycle frequency, two load locks are arranged at the input to the linear arrangement.
The disadvantage of "batch systems" is that no continuous operation is feasible. Due to their design concept linear systems require a large amount of space. In addition these systems cannot be easily integrated in a production operation because the loading and unloading stations are far apart. Such systems normally require a so-called substrate carrier that travels through the entire system. This means that a higher amount of particles may possibly be generated due to the long transport path and the complex mechanical system. In addition long, space consuming return systems for the large-surface workpiece holders are needed. An additional disadvantage is that the loading and unloading cycle is coupled directly to the system cycle.